The present invention relates to an apparatus for checking the identification data of a card for permitting access to the device once the identification data is verified, and to prevent misuse of the device once access is gained. More particularly, the present invention relates to a radio telephone or the like operated using a smart card or a memory card.
When a device, such as a telephone, is operated using a smart card or a memory card so that the user is billed based on authorization given by this card, it is important to verify the card's identification data before the access to the device is permitted, for example, before placing a call. Verifying the identification data of a card per se is known in the art and several methods have been suggested. For example, in European Patent No. 333,918, a central unit transmits an identification signal and, if this signal agrees with the identification data of the card in the telephone, the central unit permits access to the line. The line will remain open until the card is used in another location. Such an arrangement is highly unreliable because once access to the line has been gained, anyone may use the phone until the card is used at another location.
European Patent No. 301,740 and Swedish Patent No. 456,209 disclose systems where the card's identification data is checked every time an attempt is made to place a call. In EP-301,740 an identification code from a card is read into its nonerasable memory and whenever a call is placed or the apparatus is otherwise programmed, the identification code recorded in the memory is compared to the identification data of the card. If the codes do not agree, no connection is made. In SE-456,209, the checking is done with the telephone exchange. The identification code has both a fixed and a variable part. The variable part depends on the number of connections made and changes in the same manner in both the radio telephone and the telephone exchange. This system cannot be detected by an outside monitor in order to bill the user because the monitor does not know the number of calls that have been placed at any given time. In addition, the publication discloses an additional code which is used only in exceptional cases and cannot be detected easily by an outside monitor. In this arrangement, checking is performed only when a call is placed.
The arrangement described in European Patent No. 333,918 (and other similar arrangements) is the type of system currently used in the art. This system can be circumvented by using a thin plastic strip having the shape of a card. Once access is gained, the telephone remains registered with the information data of the previous card, whereupon unauthorized telephone calls can be charged to the account of the previous card. In devices using a processor card, which applied telephone-specific checking of the identification data, as in European Patent No. 301,740 or Swedish Patent No. 456,209, misuse is more difficult because a call must be placed using the correct card in order to obtain access and the card can be replaced only after the call has been connected. However, even this alternative allows misuse because a card can be used without authorization only for a moment, in which case the correct holder of the card may not notice it, or the same card may be used for simultaneously activating a number of devices. The possibility of even short term access is particularly damaging where the device accessed is an Automated Teller Machine.
Voice identification and fingerprint checking have been suggested as a possible method for preventing misuse, as in German Patent No. 3,438,106, but such systems are very expensive and unreliable. A method for preventing replacement of a card includes placing the card in a mobile slide controlled by a switch and the entire slide is pushed into the apparatus. Another similar structure is disclosed in Norwegian Patent No. 874,965, in which the card is placed in a swiveling compartment or cover, which is controlled by a switch. In these models, misuse is difficult because the card is very difficult to remove without moving the switch which controls the slide, cover, or the like at the same time. However, misuse is possible by sawing an opening into the apparatus allowing replacement of the card.